The Government today kick-started a drive to speed up a decision on whether to build new nuclear power stations.
The Trade and Industry Secretary Alan Johnson said it was time to decide what forms of energy to promote because of the "important challenges" that lay ahead.
The Government threw open public debate on its future energy policy as it launched a three-month review to seek the views of industry, pressure groups and the public.
Mr Johnson said: "I want the widest possible engagement in this vital debate. We need to look at the risks to security of supply, our climate change commitments and, to the long term, to make sure we take the necessary action. There is not a do-nothing option."
Mr Johnson published a consultation document which he said served as a " wake-up call", adding that fuel prices were on the rise and the UK was becoming an importer of oil and gas.
"In a world of heightened concerns about energy security, highlighted by the recent dispute between Russia and Ukraine, we need to look carefully at the risks of this new situation."
The minister said that, by 2020, coal and nuclear power plants currently generating almost a third of the UK's electricity were expected to be closed.
"Companies will need to decide how this capacity should be replaced. These are big investment decisions so the Government needs to provide a clear framework.
"If gas, as well as renewables, were to fill the gap, how comfortable will we be relying on imports for 80% of our supplies?"
The Energy Minister Malcolm Wicks, who will lead the review, said that, as well as energy supplies, he wanted to look at demand for electricity.
He insisted that people could do more to conserve energy, revealing that more than £740 million worth of energy was "squandered" by domestic appliances and gadgets being left on stand-by.
He said the key questions which will be posed in the coming months will include whether the Government could do more to ensure that its long-term goal of reducing carbon emissions was met.
The last energy White Paper left open the option of building new nuclear power stations and the Government made it clear today that it wanted to press ahead with as wide a debate as possible about whether to build more nuclear power plants.
Green campaigners argued that there was no need for a new generation of nuclear power stations because of the sustainable alternatives available.
The Health and Safety Executive will be involved in the review by looking at the safety of any new nuclear power stations as well as other forms of power.
The Liberal Democrat environment spokesman Norman Baker said: "This is an energy review without a purpose. The Government published a credible White Paper on the issue only a few years ago, and they should be implementing that rather than beginning another review.
"This review is simply a retrospective way of justifying the Prime Minister's wish to build a new generation of nuclear power stations, something the earlier White Paper did not recommend.
"The Government is all too aware that the UK can have an energy mix which keeps the lights on and secures supply that does not include nuclear power."
Mr Johnson told a news conference in London that the Government wanted to start the review with an "open mind", adding: "Decisions we make this year will shape our energy mix for the next 50 to 60 years. That is why it is so crucial."
The minister said the days of cheap energy had gone and he stressed that there was an important message for individuals in terms of saving energy in the house because almost a third of carbon emissions came from homes.
Mr Johnson said coal will be a more important aspect of the review than would have been the case a few years ago because of a resurgence in its importance and the development of clean coal technology.
Mr Wicks said the recent dispute between Russia and the Ukraine had sent a "shiver" down Europe's energy spine.
He stressed that the amount of power generated by nuclear stations would fall dramatically between now and the year 2020, which is why there were some "big strategic issues" to address.
The review will be completed by the summer and delivered to the Prime Minister, said Mr Wicks.